1. Field of the Invention
The present invention relates to an ophthalmological photographic apparatus for performing ophthalmological fluorescent photography.
2. Description of the Related Art
Until now, there has been known an ophthalmological photographic apparatus in which a subject is intravenously injected with a fluorescent agent to cause illumination light to excite the fluorescent agent in the vein to perform fluorescent photography on a subject's fundus. The amount of the fluorescent agent flowing into the vein of the fundus suddenly increases at a specific period of time after the fluorescent agent was intravenously injected and then gradually decreases. At an initial fluorescence stage immediately after the fluorescent agent was intravenously injected, the fluorescent agent first flows into a thick blood vessel and then flows into narrower capillary vessels, so that the flowing state of the fluorescent agent (along with the blood of the subject) drastically changes.
In fluorescent photography, it is important to observe this change in detail. Japanese Patent Application Laid-Open No. 2003-230540 discusses a system for continuously photographing a fundus image while allowing an operator to observe the fundus image at the time of the fluorescent photography.
In a later fluorescence stage in which a further period of time has passed after the fluorescent agent was intravenously injected, the fluorescent agent is delivered throughout the veins, so that a flowing state does not change so much. For this reason, in the later fluorescence stage, a change is small in the flowing state, so that continuous photographing is not necessary and observation is not very important either.
Still images to be photographed may be few in number in the later fluorescence stage, thus allowing an immediate determination of whether the photography is successful and a resulting efficient balance between a manageable number of photographs and obtaining the required information in the photographs.
However, it is difficult to determine whether the current stage is the initial fluorescence stage or later fluorescence stage at the time of photographing a still image, so that the fluorescent photography cannot be smoothly timed.